Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include <cstdio>
#include <queue>
#include <utility>
using namespace std;
typedef pair<int, int> P; typedef queue<P> Q;
int H, W, cntw, scr[52][52]; char s[52][52]; Q q;
int dx[4] = {1, -1, 0, 0}, dy[4] = {0, 0, 1, -1};
int main() {
  scanf("%d %d", &H, &W);
  for(int i = 1; i <= H; ++i) {
    scanf("%s", &s[i][1]);
    for(int j = 1; j <= W; ++j) if(s[i][j] == '.') cntw++;
  }
  q.push(make_pair(1, 1));
  while(!q.empty()) {
    P p = q.front(); q.pop();
    int x = p.first, y = p.second;
    for(int i = 0; i < 4; ++i) {
      int tx = x+dx[i], ty = y+dy[i];
      if(scr[tx][ty] != 0 || s[tx][ty] != '.') continue;
      q.push(make_pair(tx, ty));
      scr[tx][ty] = scr[x][y]+1;
    }
  }
  printf("%d\n", scr[H][W]?cntw-scr[H][W]-1:-1);
}